Device for the regulation and centering under vacuum of a filament for a wehnelt cathode



May 9, 1950 H. BLATTMANN ETAL DEVICE FOR THE REGULATION AND CENTERING UNDER VACUUM OF A FILAMENT FOR A WEHNELT CATHODE Filed May 16, 1947 ,iiwenlaw ///v/Z/ amrfnmw A/YD mwe/ 5200b Patented May 9, p" 3' v TERING UNDER VACUUM OF A FILAMENT FOR A WEHNELTCATHODE Henri Blattmann and Henri Bruck, Paris, France,

' assignors to Compagniei. Generale De Telegraphic Sans Fil, a corporation-.01 France f-- Application May 16, 1947, Serial Nb. 748,590 I I In FranceiApril 15, 1946- Sectionl, Public Law 690, August 8,1946

This invention relates to a device for the regu lation and centering under vacuum of a filament for a Wehnelt cathode.

. In the electron gun of a cathode ray tube, the

exact position of the filament with respect to the Wehnelt cathode, is of extreme importance. Now

the preliminary centering Of the filament, the

connection of the filament to the current supply conductors, as also the use of cartridges containing the filament previously centered, present numerous inconveniences due in particular to the fact that the electric connection of filament and current supply is often defective, that the car tridges are not always strictly calibrated, and the like.

a The present invention refers to a device which permits, while operating, the axial regulation of the filament, as also its centering with respect to the Wehnelt, withoutit being necessary to take any'special precautions on the mounting of the filament; on the other hand, with the device according to the invention, the preliminary evacuation of the residual gases in the filament is no longer indispensable.

The accompanying drawing represents by way of non-restrictive example an embodiment of the regulating device according to the invention.

The invention is directed to a vacuum tube with a focalized electronic pencil, that is, an electronic discharge subject to an electro-optical action of an electric or magnetic field, whose effect consists in obtaining a spot which is as precise and small as possible. The invention applies particularly to electronic microscopes, electronic an alyzers, serving particularly to reveal the internal structure of a sheet of any material over the surface of which the electronic pencil is directed, iconoscopes, and, also, oscillograph cathodes of television and measurement of instruments of high precision.

Hitherto the focalization has been obtained by acting on the field of the electronic optic by which there is lodged the emissive face of the 55 undulated wall cathode. The latter may be of the ,emissive-g filament type (that is, with direct heating); it; may also be of the indirect type, and possess a: heating filament placed in the interior of the} tube covered with an emissive substance. The Wehnelt cylinder, which is frequently termed the control electrode, is usually brought to the same potential as the cathode, or even to a more nega-; tive potential, and it acts electrostatically on the; electrons in the sense of a suitable distribution of the space charge and their concentration in the direction of its opening. Applicants provide for two regulations of the cathode, that is, inf the axial direction for the purpose of insuring aff good focalization, and in the lateral direction for the purpose of preventing deformation of the spot, and "particularly for preventing astigmatisnn These regulations can only be carried out cor rectly with the help of a constant supervision of" the spot. Hence it is necessary to carry them out in a tube under operation, and of resolving the diificulty of displacement in the interior of the cathode without compromising the vacuum of" the tube. 1 v

Referring to the drawing in detail the filament 2 is mounted on an insulating support Ill, for ex ample of'steatite, which is at the extremity of a; rigid metallic tube l in whichare arranged the two current supply conductors 3; the latter terminate ,at two passage conductors 9 which pass throu h e p rt ti t s a lw fih the .Wall of the enclosure of the vac'uum'tube'i p .The tube I has a spherical reinforcement! which allows the axial guidance thereof or the rotation in the Wehnelt cylinder IS. The centering of the whole about a point 0 located on the axis of the Wehnelt cylinder is carried out externally and even during the operation of the vacuum tube, due to a spherical sliding path 5 having 0 for its centre, and manipulated by screws such as 6, arranged all round the part II which supports the filament carrier tube I and which is connected to the body of the vacuum enclosure I2 by the intermediation of a flexible l3. Finally, the screw 1 also manipulated from the outside by means of an operating rod I5 acting through an undulated diaphragm l4, serves for the axial regulation 0'! the filament, allowing its displacement along the axis of the Wehnelt cylinder I6.

If the undulated or corrugated diaphragm I3 is sufiiciently rigid, the spherical swelling 4 0f the tube I may be omitted, and the regulation may be proceeded with as before by again acting on the screws 5 and 1. For the sake of simplificationare thus carried outindependently'one' oftheother. Furthermore, the device is regulated during the running of the vacuum tube, seeking, for

. example, to obtain the maximum brilliance of the track or mark of the beam-.onthefluorescent screen. V v

While we have described our invention in one'of its preferred embodiments we realize: thatmodi' fications in construction may be made and. we desire that it be understood that-n limitations: upon our invention are intended other than. may be imposed by the scope of the appendedtcl'aims.

What we claim is:

1. In a. high vacuum apparatus of the type using a focalized electronic beam, a vacuum tight" envelope having an immobile part, a rigid=..movablepiece' having both lateral and axial move: men-t tormingl a part of said envelope and connectedpermanently to the immobile part of the envelope through a flexible and deformable vacuum-tight piece, an em'i'ssive cathode inside oi-the said. envelope. rigidly fastened to the said movable. piece, and. means associated. with the saidenvelope and. exposed externally thereto for controlling the position of the. said movable piece employed, in place or a claim 2 in which said control cylinder has an aperture located axially thereof opposite the cathode: for. emitting electrons; in a controlled beam. l '7 5. A high vacuum apparatus as set forth in claim 2 in which the means associated with said envelope and disposed external to it act on said movable. piece so as to displace it to either of tvmseparated. positions, and in which separate means are associated with said envelope external thereto: and actingdi'rectly on'the movable piece ibr displacingthe movable piece in a transverse direction. I 1

1 6.. In. ahigh. vacuum apparatus of the type using a. iocalized electronic beam, a vacuum-tight envelope having an immobile'part, a rigid movable member having both lateral and axial movement forming a part of said envelope, an extensibleand flexible corrugated vacuum-tight so as-to displace it hothlaterally and axially relativelto. the axis or the apparatus. 7 V

. 2.. a high vacuum apparatus of the type afocalizedelectron-icbeam, a vacuum-tight envelope having an immobile part, a rigid. movable. piece having both lateral. and axial movementiorming. apart of said. envelope and connected. to the immobile part of said. envelope by means of aflexible. and deformable vacuum.- tight piece, an electronic gun inside oi the said envelope comprising a'mobileremissive cathode "and a fixed control cylinder surrounding said cathode. means for supporting said cathode rig"- idly to the said movable piece-of the envelope, and means associated with the said. envelope and disposed externally'thereto for controlling.

the position-of. the said movable piece so as to regulate laterally'and axially the cathode position. relative to the cylinder. 7 z

;.3'. A, high vacuum. apparatus as set forth in. claim ain'which theimmovable part. and the movable piece oi. said envelope are connected. through a corrugatedlsl'eeve which. is extensible and flexible Y 41, A high. vacuumv apparatus as set forth in axis of the said control.

membrane of a sleeve form connecting said memher. to. the immobile part. oi the envelope, a. control cylinder for an electronic gun. in the inside of the said envelope, said control. cylinder hav-' and. outside of said. envelope for mounting; said support piece, and a plurality of regulating means.

REFERENCES CITED The following references are. of. record. in. the file of this patent: V UNITED STATES PATENTS Number Name Date- 2 2U8, 406 Benedict July" 16, I940; -2.;218;,886 Krause Oct. 22,1940- '.2,i30l,955 Krause V Nov; 17', 1942 2,516,318 Hotine Feb. 27', 1947 21424,?

Bachman et al July'29, 1947 

